diyAudio Forums Archive - Kofi Annan in: "300beee!" or "Kofi Gets a Toy"

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Kofi Annan in: "300beee!" or "Kofi Gets a Toy" - Click HERE for Original Thread

Kofi Annan

So the story goes, me and Mrs. Annan are about to have a bit of a windfall. Its never happened before to the Annans and probably won't happen again, so its time to think big, act irrationally and ooze irresponsibility. That means I get a toy.

Given that, the question is what do I build?

Now, I still have my hooks in the Bevois Valley push pull amplifier-- I'll probably order parts for that really soon. But the fact remains that I think I could tackle a project that would require more financial resources as long as I act before Mrs. A changes her mind.

I have thought about a 300b SET for some time now, and I think I'd maybe like to build a pair of monoblocks. The question, of course, is which design?

Now I know I'm going out on a limb here asking for people on DIYAudio to espouse an opinion, but maybe just this once you could let me know how you really feel.

In a post earlier, I mentioned the possibility of working on a 300b and Thorsten's "Monkey on a Stick" was mentioned as being a frontrunner. Another possibility, of course, would be the FI Primer or the Angela Instruments version.

Still, I'd like to hear what you think would be best for me to rush headlong into without regard to my future financial well being. I'd say I could spend about $1K or so on the project, although Mrs. Annan and I have not discussed the dollars (so don't tell her, OKAY?!?).

Can I get a witness?

Kofi

Robski666

Hi Kofi,

I thought tubelab had a 833 project going seemed interresting and you could offset your heating bill substantially thus saving more money in the future!

apart from that I have no SET experience but good on ya ;o)

Robert

Kofi Annan

Thanks for keepin' it real, Robski666! I'll check it out.

As far as the 300b goes, I think the drd 300b in this thread is really interesting. I was pointed to this one before, but I never acted-- sometimes it takes me a while.

So, any thoughts on this one? I built Thorsten's Phono Pre and I absolutely love it, so this might be a good fit for me.

Kofi

Gluca

Mr. Annan

everyone built a 300B once in lifetime. Is it going to be you the next one? I remember a nice and recent project by Jim Doyle ... the guy used a cheap & strong & politically correct 811A (class A2) parafeed at 450V B+.

Mr. Annan will you be the next one?

Gianluca

ligascon

Hey Kofi...

Please do yourself a favour and build the d3A/300B DRD thingie. It's really worth it...

Just my 2 cents.

Best regards,

Luis

Bas Horneman

quote:

I think the drd 300b in this thread is really interesting

As good as any out there in my opinion. The thing is that once you have the 300B's, powertransformer, chokes, output transformers, psu caps.. you can go ahead and change the driver configuration to see which you like most...without any big expense... then when you like what you have .... you can start adding a trick or tweak...

At the moment I am playing with a d3A choke loaded driver...simple, effective and good sounding. The drd types are the exception really in that they need higher voltages than average...so once you have power transformers that have multiple taps..the 300b world is your oyster.

Tweeker

Well, if your looking for pearls such as this, hamfests are fabulous places to visit. You wont find many 300Bs, but all sorts of iron and glass baubles to snatch from the deep.

Robski666

Hi Kofi,

sorry about the 833 thing i couldn't help myself thinking SET and remembering the pictures Greorge posted of his 833 looked awsome, and I was just trying to help out with justification for spending more money, ;o)

I also looked at Welborne site and my they are expensive and the drb isn't that complex. I kinda like the version in the link although if it's SET why use a pentode as a driver?

Robert

Kofi Annan

Sorry for the delayed response...

quote:

everyone built a 300B once in lifetime. Is it going to be you the next one?

Let's hope Mrs. Annan doesn't have a change of heart.

quote:

Please do yourself a favour and build the d3A/300B DRD thingie. It's really worth it...

Luis! Good to have a response from you! I have questions:

First, where did you get your motor run capacitors and is there a reason for paralleling these rather than going for one value that's close to the sum of the parallelled caps? Also, is the amorphous OPT really necessary or can I get away with the non-amorphous? In addition, is there a way I can get the word "amorphous" into more conversations? Its a cool word.

Amorphous.

Also, the D3a driver tube may be a bit tough to find. Any recommendations on a substitute?

quote:

That's what I'm talkin' 'bout!

quote:

sorry about the 833 thing

Why be sorry?!? I love the open exchange of new suggestions. Not in a like-I-love-Mrs.-Annan-after-I've-had-a-couple way, but its love just the same! Thanks!

Also, instead of monoblocks, I may try and cut a corner and get one power supply for the whole shebang. Would I just need to increase the mA rating for the power transofrmer?

Bas Horneman

quote:

Also, instead of monoblocks, I may try and cut a corner and get one power supply for the whole shebang. Would I just need to increase the mA rating for the power transofrmer?

Basically yes....that is all there is to it. Don't forget that you need enough juice for the filaments as well. Not just for your b+.

Amorphous, well yes..you can skip the amorphous transformers..there are many factors that make for a good sounding output transformer...the core is only one of those factors.

But I suspect once your amp is up and running..you will start wondering how big an improvement it would be to get amorphous...In that case go straight for the amorphous...if you are a headstrong, balanced sort of person. In other words not an audiophile but a music lover..force yourself to accept that a wonderful sounding 300b amplifier need not sound just that 5% (if that) better than it already is (maybe not even better but different) and spend the extra cash on "software" to feed into your amp...or a nice gift for Mrs. Annan.
:D

Amorphous....amorphous.....and I sing to myself...what a wonderful word..

ligascon

Hi Kofi,

About the caps you can go with one of the same value of the parallel caps in the schematic. I got my caps at cricklewood electronics in London...I'm sure that you could find some GE motor run on ebay for good price also.

Yes amorphous is a cool word...amorphous, amorphous, amorphous.

In spanish it's similar to ugly or deformed...but hey, it's sounds just beautiful on my system. As I said on the original thread, I didn't try anything else. I could only trust the general buzz about this type of transformer and went with it. I totally happy by the way. One observation; the sound is still opening up...I guess that the run in time is quite long with this kind of core.

Siemens d3A show up regularly at ebay, sometimes for pretty good prices (I just grabbed some for 7,50$ each, I don't know if I should be advertising this!)

Good luck with the planning ordering etc...by the way kofi, thanks for your thread regarding Thorsten's phono. I got tons of great info about hands on building, in fact I'm currently collecting the parts to build Thorsten's "el phono cheapo" let's see who finish first!

Bas sorry, I still have to send you some stuff.

Take care. Best whishes for the new year.

Luis

Bas Horneman

Hi Luis,

quote:

Bas sorry, I still have to send you some stuff.

Luis, sorry, I still have to send you some stuff too.. ;)

Regards,
Bas

Kofi Annan

quote:

Basically yes....that is all there is to it. Don't forget that you need enough juice for the filaments as well. Not just for your b+.

Thanks!

quote:

About the caps you can go with one of the same value of the parallel caps in the schematic. I got my caps at cricklewood electronics in London...I'm sure that you could find some GE motor run on ebay for good price also.

Good deal! Thanks!

quote:

Siemens d3A show up regularly at ebay, sometimes for pretty good prices

Still looking for the good prices, but I'm patient...

quote:

by the way kofi, thanks for your thread regarding Thorsten's phono. I got tons of great info about hands on building, in fact I'm currently collecting the parts to build Thorsten's "el phono cheapo" let's see who finish first!

Don't thank me-- thank Thorsten. I'm just the guy who asks the questions.

I've had mine finished for some time and I absolutely love the sound. Try it. You won't be disappointed. Oh-- and let us know when you finish and what you think.

More questions:

Where did you get your PSU transformer? Also, what about the common mode choke on the filament? Is it a Plitron? No? Well what is it then?!? ANSWER ME!?!

Oh.. right... gotta give you time to respond. Sorry.

Kofi

Kofi Annan

Also, what's the inductance of the 15mA choke load for the D3a anode? Ain't that a cool sounding question?

Kofi

Tweeker

Amorphous!

I just like the word. It gives me confidence. Amorphous ... amorphous. It's got a sort of woody quality about it. Amorphous. Amorphous. Much better than `newspaper' or `litterbin'.

Frightful words.

Perfectly dreadful.

Ugh! Newspaper! ... litterbin ... dreadful tinny sort of words. Tin, tin, tin.

Sausage! :spin:

Sausage ... there's a good woody sort of word, `sausage' ... amorphous.

Cheap transformers, 480V industrial and choke input might work.

Nordic

Ok Tweeker, I need you to keep your hands where I can see them, now move away from the ashtray... slowly!

And yes Kofi, thats exactly the kind of questions the UN should spend more time on.

Bas Horneman

quote:

Ok Tweeker, I need you to keep your hands where I can see them, now move away from the ashtray... slowly!

Ja...nee....ek trust hom so ver as wat ek 'n blerrie sherman tank kan gooi...en buitendien het hy regtig genoeg gehad!

Tweeker

Shermans, they light up every time! :hot:
They are easy to drive! :captain:
Hydromatic luxury! :cloud9:

ligascon

Hi all,

About Thorsten's phono...well yes, we all should thank him (I did already) but I also thank you for having the guts to ask all the questions that I would be afraid to ask. You're the man.

The mains transformer is from diyparadiso in Belgium but I'm thinking a new one from vt4c.com

Please note that filament supply for the d3A is supposed to be 6,3 Volts. Thorsten advices to run in at low 5,5. See, as I told you before I was afraid to ask why and just did it. I'd like compare how the sound changes using different voltages, say 6, 6.1 and 6.3. The common mode choke is from rs components.

Right now I'm thinking of trying Guido Tent's filament supply for the 300B...just to see how does it sound.

The inductance for the Lundahl anode choke is listed at 270H in the factory PDF. Look it up on the factory site. I ordered another couple anode chokes from tribute in the netherlands...it's supposed to be a big improvement but it's going to take awhile to deliver.

Best wishes. I'll let you know when I finish the phono stuff...

Luis

dave dove

kofi annan

i thought long and hard
before posting for you
i see you have almost decided
and it probably is good
but is it this good?

unfortunately i can't say amorphous
so i say PARTRIDGE

PARTRIDGE

PARTRIDGE

PARTRIDGE

PARTRIDGE

PARTRIDGE

looking forward

dave dove

Sheldon

If you are not certain, this may be the one. I haven't built it or heard it, but it can be configured for many different output tubes - so go ahead and wallow in indecision with no regrets. http://db.audioasylum.com/cgi/m.mpl...ten&r=&session=

I think it is sold as a kit by diyhifisupply.com. Maybe they sell just the transformer too.

Sheldon

Kofi Annan

quote:

Originally posted by ligascon
About Thorsten's phono...well yes, we all should thank him (I did already) but I also thank you for having the guts to ask all the questions that I would be afraid to ask. You're the man.

Wow. I didn't think I had any "The Man"-like qualities, but apparently endless redundant, inane, elementary and redundant questions gets you in. Looks like the bar's been lowered.

quote:

The mains transformer is from diyparadiso in Belgium but I'm thinking a new one from vt4c.com

Can't seem to find a transformer with these specs on DIYParadiso.com, but I'd bet that Jack at Electra-print could wind one. Hmmm... that vt4c.com looks like an interesting site. Have you ever ordered from them?

quote:

Please note that filament supply for the d3A is supposed to be 6,3 Volts. Thorsten advices to run in at low 5,5. See, as I told you before I was afraid to ask why and just did it.

Good idea.

quote:

The common mode choke is from rs components.

Got it. Should be 7.5mH, right?

Dave-- this design looks interesting, but I think I'm gonna stay with the DRD.

quote:

Wow! That's pretty cool. Unfortunately, its probably more than I can spend given the increased number of parts. Mrs. Annan's a nice girl, but not that nice.

Any ideas on the voltage rating for the paralleled caps in the amplifier circuit? I want to make sure that I don't get underrated caps.

Also, Lundahl has the LL1623 rated at a maximum primary voltage of 270V and a primary impedance of 3K, which is different than the specs listed for this OPT on the schematic. Now, I notice that these can be wired in, like, a zillion different ways, so there must be a way to wire the 1623 to get 5.6K primary with 8R out, right?

Also, how can this be rated at 270V when we know there's 620V running through it? I know, dumb question-- but WHY is it a dumb question?

Kofi

Tweeker

Thats primary signal voltage, VAC RMS.

Isolation is 3 kV between primary and secondary, 1.5kV between windings and core.

Sheldon

quote:

Originally posted by Kofi Annan
Wow! That's pretty cool. Unfortunately, its probably more than I can spend given the increased number of parts. Mrs. Annan's a nice girl, but not that nice.

Any ideas on the voltage rating for the paralleled caps in the amplifier circuit? I want to make sure that I don't get underrated caps.
Kofi

Actually you can do this just as you would any other version, no extra parts. Three substituted parts - an adjustable cathode resistor instead of fixed, and some different taps on the OPT's and power transformers. If you ordered them wound, the extra taps wouldn't cost much more. Might be a bit much for an early project, but as you say, it is kinda cool.

For a specific answer, it would require knowing which caps. Generally, the caps have to be rated for the voltage they will see under any circuit condition. Maybe a 20 percent safety margin beyond that is a good idea. Parallel caps require the same rating as a single caps. Caps of the same type and value can be put in series. Two caps in series split the voltage in half, but as you know from your dealings in the U.N., they may not be inclined to play nice and share equally. So you have to send in some troops in the form of a resistor divider to make sure they play nice. You can see an example of this in Thorsten's power supply as shown in the referenced thread.

Sheldon

ligascon

quote:

Looks like the bar's been lowered

You dont even know...I lower it every other time, sometimes even without opening my mouth...

quote:

that vt4c.com looks like an interesting site. Have you ever ordered from them?

Yes, I ordered some tube sockets and silver wire. Really serious and no problems at all.

quote:

Should be 7.5mH, right?

Yes

quote:

Any ideas on the voltage rating for the paralleled caps in the amplifier circuit?

The Ducati Motor Run that I got are rated 450 VAC...that should give you some safety margin even if I run B+ at 650 DC Volts.

quote:

there must be a way to wire the 1623 to get 5.6K primary with 8R out, right?

Yes, it�s listed as ALT B on the factory PDF. The Lundahl part is what I used but you should feel free to try any other brand. I�m sure that either electra-print or magnequest should have suitable chokes and trannies...it�s your call.

Good luck with all the preparations. Take care,

Luis

Kofi Annan

quote:

Thats primary signal voltage, VAC RMS.

Thanks!

quote:

Yep. Kinda cool, but might be too much for me on this go 'round.

quote:

The Ducati Motor Run that I got are rated 450 VAC...that should give you some safety margin even if I run B+ at 650 DC Volts.

OK-- this is confusing to me since I thought that I would need to multiply the 450VAC x 1.414 to get a total DC voltage rating of ~636V, which would not accommodate the 650VDC. I have found some 420VAC rated motor run caps that I would have like to have used in the PSU, but my calculations indicate that this would only be ~593VDC-rated and would not work.

Of course, nothing in the universe have proven more consistently wrong than my calculations, so are the motor run caps rated conservatively or am I not calculating this right?

quote:

I figured that one out after I posted... thanks!

I'll probably stick with the Lundahl OPT, but I may mix it up a bit with the PSU and chokes.

Also, did you use motor run caps in the amp circuit, the PSU or both?

Yours in ignorance,
Kofi

Sheldon

quote:

Originally posted by Kofi Annan
so are the motor run caps rated conservatively or am I not calculating this right?
Kofi [/B]

Yes, generally so. They are designed for pretty severe AC duty, so the AC ratings reflect that. example: http://www.cornell-dubilier.com/misc/hot.htm

Sheldon

Kofi Annan

Thanks!

Even more questions:

So, does that mean I could safely use a 370VAC-rated motor run capacitor for the power supply?

Also, can you(ze) tell me how many mA I the circuit consumes or what would be the recommended mA rating for a power transformer? I may be having one wound and I know that this question will come up.

Kofi

Sherman

quote:

Originally posted by Kofi Annan
Thanks!

...
So, does that mean I could safely use a 370VAC-rated motor run capacitor for the power supply?
...
Kofi

If you wish to be conservative multiply your AC rating by 1.4 to get the DC rating. In this case 518 VDC. And that is working voltage. They can take higher voltages for short periods of time (as when charging up).

I've had motor run (and make sure they are motor run not motor start) caps in my SE KT88 monoblocks for about a year now. The PS voltage is 425, max voltage on the caps as the PS stabilizes over the first 30 seconds or so is 560. I think the caps work great.

Having said all that I've been told I can safely double the AC rating for DC use but I'm too much of a coward... er, uh, I mean conservative, yeah, that's it; conservative, with electricity to try that (so far).

Sheldon

quote:

Originally posted by Kofi Annan
Thanks!

Even more questions:

So, does that mean I could safely use a 370VAC-rated motor run capacitor for the power supply?

Also, can you(ze) tell me how many mA I the circuit consumes or what would be the recommended mA rating for a power transformer? I may be having one wound and I know that this question will come up.

Kofi

Quite likely on the 370 caps. But if you're worried about it use 440AC caps. It's a very common motor run value.

How many ma? Depends on the circuit, but no higher math required here. Just add up all the current sinks - bias for each tube and any bleeder resistors, etc.. If you are not sure of the transformer quality, overrate by 20%. If you have one wound, just give the winder your circuit.

Sheldon

Bas Horneman

quote:

How many ma?

150mA is usually more than enough. With most 300b's drawing around 70mA and the driver say 8mA-45mA ..plus maybe a little by a bleeder here or there.

So anything from 150mA to 400mA is fine. For your HT/B+. (Mono)

The filaments per monoblock. Say 2,5-0-2,5V/3A for the rectifier tube.
5V/2A for the 300B perhaps an extra 2.5V/2A tap so that you could add to the 5V tap in case you want to upgrade or try something like Guido Tent's heaters. (You need a little voltage headroom for the circuitry)

3,15-0-3,15/2A or whatever your driver tube requires. Et voila! 0 goes to elevated bias for minimal noise.

And as Lynn Olsen always says..try to get an electrostatic screen between primary and secondary. It only adds a couple of dollars but you prevent unneccesary noise right from the word go. Almost a free lunch so to speak.

Kofi Annan

quote:

Having said all that I've been told I can safely double the AC rating for DC use but I'm too much of a coward... er, uh, I mean conservative, yeah, that's it; conservative, with electricity to try that (so far).

I'd be a bit scared too. I think I'll look for a 440VAC.

quote:

So anything from 150mA to 400mA is fine. For your HT/B+. (Mono)

Thanks!

Now I have some power supply questions:

Attached is the PSU that Luis uses and I think its neato, so I'd like to implement it. What my dim brain has noticed is that somehow, he's using a 250V secondary to get 620VDC out. I'm thinking that this means maybe the diodes at the plates of the 274A rectifier are acting as a voltage doubler and the bootstrapping (is this the right term?) of the 5.5V supply is helping increase the voltage as well.

It could just as easily be pixie dust, though.

Also, I know that the 274A is one hell of a rectifier, but its also got one hell of a price tag. Could I use another rectifier here without much modification to the PSU circuit?

Also, anyone ordered parts from Jac Music before? They have a pair of TJ "Full Music" 274As that aren't go-knock-over-a-liquor-store expensive (about $150US), so they may be the ticket.

Kofi

Sheldon

quote:

Originally posted by Kofi Annan
Attached is the PSU that Luis uses and I think its neato, so I'd like to implement it. What my dim brain has noticed is that somehow, he's using a 250V secondary to get 620VDC out. I'm thinking that this means maybe the diodes at the plates of the 274A rectifier are acting as a voltage doubler and the bootstrapping (is this the right term?) of the 5.5V supply is helping increase the voltage as well.
Also, I know that the 274A is one hell of a rectifier, but its also got one hell of a price tag. Could I use another rectifier here without much modification to the PSU circuit?
Kofi

That transformer is mislabled. It's actually a 250-0-250 center tapped transformer. But the center tap is unused, so the sections are in series, giving a 500v secondary. Since it's used that way, it should be labeled 500V.

I think that the 274b is the same internally as the 274a (confirm that with the experts here). If so, the 274b might be the better choice, since I believe its pin configuration and socket (octal) makes it easier to sub in other rectifiers. The 274b has a higher internal resistance than most of the substitutes, so you would get higher B+ by changing to something different. Also, some of the other tubes will tolerate a larger input cap. The best way to look at this is just plug that circuit into PSUD and play. You can't model the hybrid rectifier directly, but you can model a SS bridge and a tube bridge and split the difference in output voltage.

Sheldon

Kofi Annan

quote:

Wow! Thanks! I coulda made a bad mistake there.

So are the secondaries really 5V and 5.5V respectively? These seem like odd values. If they are, that's fine-- I can have one wound, but I'd just like to know.

quote:

I think that the 274b is the same internally as the 274a (confirm that with the experts here). If so, the 274b might be the better choice, since I believe its pin configuration and socket (octal) makes it easier to sub in other rectifiers. The 274b has a higher internal resistance than most of the substitutes, so you would get higher B+ by changing to something different. Also, some of the other tubes will tolerate a larger input cap. The best way to look at this is just plug that circuit into PSUD and play. You can't model the hybrid rectifier directly, but you can model a SS bridge and a tube bridge and split the difference in output voltage.

Good news! I'll wait for the verdict from the experts, but I might just go ahead and do the 274A anyway. I always cut corners on these projects and just once I might build to spec...

Also, how about these for PSU motor run caps. Will they be OK?

Kofi

stalker

quote:

Also, anyone ordered parts from Jac Music before?

I have. Jac is a nice guy, he has a love for tubes and prices are fair.
Recommended.

Kofi Annan

quote:

I have. Jac is a nice guy, he has a love for tubes and prices are fair.

Thanks!

Now about those motor run caps...

Tweeker

Looks like a good deal, 440VAC motor run caps are more than up to it.

If using tube rectification and capacitor input, check tube ratings, you may want to use a smaller cap for the first section or series resistance.

Kofi Annan

quote:

Looks like a good deal, 440VAC motor run caps are more than up to it.

Alright!

quote:

If using tube rectification and capacitor input, check tube ratings, you may want to use a smaller cap for the first section or series resistance.

The PSU has a 4uF cap in the first section, which I believe is appropriate for the 274A rectifier.

OK-- in the interest of understanding this design, I have noticed that the plate is putting out 60mA (quiescent current, I guess) at 599V, but that seems like waaaay too much voltage. I have been trying to plot the loadline and for a 5.6K primary and a 60mA Ic, we should be at about 336V, but we're not.

So the question is, how dumb is my next question, which is how can we have almost 600V at the plate of the 300b?

I know I'm gonna get slapped for this one and I'm gonna deserve it too, but I gotta know.

Kofi

Kofi Annan

Here's the original schematic, for your reivew.

Kofi

Sheldon

quote:

Originally posted by Kofi Annan

OK-- in the interest of understanding this design, I have noticed that the plate is putting out 60mA (quiescent current, I guess) at 599V, but that seems like waaaay too much voltage. I have been trying to plot the loadline and for a 5.6K primary and a 60mA Ic, we should be at about 336V, but we're not.

Kofi

Actually you are at about 336V. The question when talking about voltage is; voltage with respect to what? Voltage is the potential between two points. When we are talking about plate voltage, we are talking about the voltage between the plate and the cathode. Your cathode is at 249V above "ground". Your plate is at 599V above ground. So your plate voltage is 599V minus 249V, or 350V.

Sheldon

Kofi Annan

quote:

Actually you are at about 336V

D'OH!

Kofi

ligascon

Hi all,

quote:

I know that the 274A is one hell of a rectifier, but its also got one hell of a price tag. Could I use another rectifier here without much modification to the PSU circuit?

Kofi I�m currently using Valve Art 274Bs that I bought from Jac Music at a real fair price (something like 20 EURO each). Can�t tell the difference in sound with the chinese mesh 274As. 274A and 274B are the same tube with different base.

quote:

It is a 250-0-250 Transformer. I thought that it was OK to draw it like that...

Best regards,

Luis

Sheldon

quote:

Originally posted by ligascon
It is a 250-0-250 Transformer. I thought that it was OK to draw it like that...
Luis

I apologize if my comment regarding the transformer label seemed critical. That was not my intent. It's just that in your application, it is not a CT transformer. Just trying to help clear up some confusion. Experienced readers would have no problem with your label, and would recognize that it started out life at a CT.

Sheldon

ligascon

Hi all,

quote:

Just trying to help clear up some confusion

No problem at all, thank you for doing just that....

Cheers,

Luis

Kofi Annan

quote:

Woo hoo! Glad that worked out-- saved me a bundle. I ordered two 274Bs today as well as the motor run caps for the PSU. I need to spread the cost over time, so that's all the buying I can do for a while.

quote:

It is a 250-0-250 Transformer. I thought that it was OK to draw it like that...

I'm sure its OK-- I'm just a dumbass.

quote:

Experienced readers would have no problem with your label, and would recognize that it started out life at a CT.

See?

Having a tough time getting Jack from Electra-print to respond to my request for a hand-wound PSU transformer, but I'm paitient. Any other winders you geeks would recommend?

Also, anything against using wirewounds for (what I think is) the voltage divider (with the paralleled 7K5 resistors) network in the audio circuit? Any what's the 100R pot for? Is this to adjust the fixed bias?

Wow. There's some whoppong dumb questions in here I'm sure. Go ahead. Give it to me. I can take it.

Kofi

ligascon

Hi all,

quote:

what's the 100R pot for?

It adjust the bias voltage for the d3A and hence the voltage supplied to the d3A and the 300B anodes. If you increase the bias voltage your d3A will work at a higher anode voltage and your 300b at a lower and the opposite. it sure comes in handy to balance things out...right now I�m running the d3A at about 2,11 Volts bias which gives me something like 175 Volts on the d3A anode and around 345 on the 300B. I like the sound this way.

quote:

anything against using wirewounds for the paralleled 7K5 resistors?

Nothing that I can see. Just try to use a good quality metal film or tantalum for the 47K input and a carbon type for the d3A grid stopper (Bradley or Riken) The rest will make a difference but I don�t think it�s so critical.

Good luck and best whishes. Regards,

luis

Kofi Annan

quote:

Got it! Thanks!

quote:

Just try to use a good quality metal film or tantalum for the 47K input and a carbon type for the d3A grid stopper (Bradley or Riken) The rest will make a difference but I don�t think it�s so critical.

Will do.

Well, you know... more questions. I'm really trying to make this a true learning experience, which will be trying for the DIYAudio community but I have faith in you(ze). So, in the interest of learning...

I thought that the 300b was supposed to see between a 3K and 4K plate load, but it looks to me like its seeing the 5.6K primary of the OPT and, therefore, a 5.6K load. Since matchematically, it must be looking at a 3.5K load to make 60mA at a 21V voltage drop, I know this is wrong, but I don't know why.

Also, I thought that the proper bias resistor to set the cathode voltage at 249V would have been about 5.8K, but the total resistance that the 300b cathode sees to ground looks to be about 4.8K. Once again, this is wrong, but I don't know why.

Also, my cousin has been touching me on the leg while nanny is away. I know this is wrong, but I don't know why.

Can ya help?

Kofi

Sheldon

quote:

Originally posted by Kofi Annan
Having a tough time getting Jack from Electra-print to respond to my request for a hand-wound PSU transformer, but I'm paitient. Any other winders you geeks would recommend?Kofi

Jack is old school. He's been very responsive on both my orders, but you have to call him. He doesn't respond as well to e-mail.

Sheldon

quote:

Originally posted by Kofi Annan
thought that the 300b was supposed to see between a 3K and 4K plate load, but it looks to me like its seeing the 5.6K primary of the OPT and, therefore, a 5.6K load. Since matchematically, it must be looking at a 3.5K load to make 60mA at a 21V voltage drop, I know this is wrong, but I don't know why.

Also, I thought that the proper bias resistor to set the cathode voltage at 249V would have been about 5.8K, but the total resistance that the 300b cathode sees to ground looks to be about 4.8K. Once again, this is wrong, but I don't know why.

Also, my cousin has been touching me on the leg while nanny is away. I know this is wrong, but I don't know why.
Kofi

The transformer load has nothing to do with the bias current, which is DC, except for the DC resistance of the transformer. The load here refers to the reflected impedence - (primary turns/secondary turns)squared, times speaker impedence - for AC. I don't know much about ideal loads for 300b's but if your speakers are typical, they would have an actual impedence closer to 6 ohms, bringing your load for that transformer in the 3-4k range.

The 1k bias resistor would have a drop of 60v at 60 ma. This seems reasonable, as after that resistor, current is drawn off for the input tube's plate. This would indicate an input tube voltage of 249 - 60, or 189V. The actual voltage shown is 177 at the input plate, so the difference is probably in the resistance of the DRD choke. That current does not go through the paralleled 7.5k resistors, but reenters the stream below them. That current is shown as 15ma through the choke and 10ma through the input tube. They are in series and therefore must be the same, so one of those is wrong. No big deal, let's split the difference and call it 12.5V for convenience. So you have 60ma through the 1k for a drop of 60V, and 60-12ma, or about 48ma through the 3.75k (parallel 7.5k), for a drop of 180V. Now bring the two current streams together after the 3.75k and send the total 60ma through the 100 ohm resistor for 6V. So, 180 added to 60, plus 6, gets you 246. or close enough for tube work.

Can't help with the cousin though.

Sheldon

Kofi Annan

quote:

Jack is old school. He's been very responsive on both my orders, but you have to call him. He doesn't respond as well to e-mail.

Very old school. I talked to him for about a half an hour this evening and he had lots of opinions about modifications to the DRD design, none very good, I'm afraid.

Anyway, he's going to wind me some power transformers and possibly a pair of OPTs, but I'll probably have to wait a while. He just got back from CES and he's pretty backlogged.

quote:

Wow! That's good information!

quote:

The 1k bias resistor would have a drop of 60v at 60 ma. This seems reasonable, as after that resistor, current is drawn off for the input tube's plate. This would indicate an input tube voltage of 249 - 60, or 189V. The actual voltage shown is 177 at the input plate, so the difference is probably in the resistance of the DRD choke. That current does not go through the paralleled 7.5k resistors, but reenters the stream below them. That current is shown as 15ma through the choke and 10ma through the input tube. They are in series and therefore must be the same, so one of those is wrong. No big deal, let's split the difference and call it 12.5V for convenience. So you have 60ma through the 1k for a drop of 60V, and 60-12ma, or about 48ma through the 3.75k (parallel 7.5k), for a drop of 180V. Now bring the two current streams together after the 3.75k and send the total 60ma through the 100 ohm resistor for 6V. So, 180 added to 60, plus 6, gets you 246. or close enough for tube work.

Even better! I think the 15mA on the DRD choke is a rating and not the actual amount of current drawn, but I probably have that wrong.

Thanks, man. Your description of the current flow really, really makes a lot of sense to me. Tell me something 5.2 million times and I'm likely to get it.

OK-- now for a really dumb one. Since this is a directly-heated triode, the filament voltage and the 1K resistor will both need to be connected to the same place, right? In other words, the filament voltage is tied to the proper pins (the two for the filament) and the cathode resistor is tied to one of the filament pins, right? Does it make a difference which of the filament pins the cathode resistor is tied to?

Hey-- the right answer gets you a date my cousin. She ain't a looker, but she knows where to touch!

Kofi

arnoldc

i'll touch the left leg of your cousin, i mean, the negative side...

no hum balance bot? no resistor pair? i know you're going dc but, it think it should still help.

ps. now how about your cousin? tell me more :D

pps. you're going DRD right? if you don't use hum pot or resistor pair, it will increase your bias voltage by 5V (filament voltage) and may screw up (a bit) all those computations above. but i won't get really anal about it :D

Sheldon

quote:

Originally posted by Kofi Annan
Even better! I think the 15mA on the DRD choke is a rating and not the actual amount of current drawn, but I probably have that wrong.
Kofi

You're right, that's very likely the case. I shoulda caught that.

quote:

Originally posted by Kofi Annan
[B
OK-- now for a really dumb one. Since this is a directly-heated triode, the filament voltage and the 1K resistor will both need to be connected to the same place, right? In other words, the filament voltage is tied to the proper pins (the two for the filament) and the cathode resistor is tied to one of the filament pins, right? Does it make a difference which of the filament pins the cathode resistor is tied to?
Kofi [/B]

That's what the schematic shows. It might make a little difference which side, but I think that' something you'd actually have to try. If I were doing it, I think I'd do as ArnoldC suggests and put a couple of 100ohm, 1watt resistors in series across the winding, and connect the 1k resistor between them. But maybe that's just being anal.

Sheldon

ligascon

Hi people,

quote:

I think the 15mA on the DRD choke is a rating and not the actual amount of current drawn

That�s correct. Sorry if it appears confusing on the schematic.

By the way Kofi, I�m trying to find Thorsten�s email where he details the ins an outs of the design...I�ll post it (if he doesn�t mind) I�m sure that it won�t anwser all of the questions but it will help you out understanding the whole thing.

Best regards,

Luis

Kofi Annan

quote:

You're right,

First time for everything. I'm callin' my mom.

quote:

Why would it make a difference with the resistor divider in there? Just keeping things in balance?

quote:

By the way Kofi, I�m trying to find Thorsten�s email where he details the ins an outs of the design...I�ll post it (if he doesn�t mind) I�m sure that it won�t anwser all of the questions but it will help you out understanding the whole thing.

Yeah! That would be great!

Thanks for all the help. More questions to follow.

Kofi

Kofi Annan

More questions (that was fast!):

The 5.5V secondary on the PSU, is that for real? When I talked to Jack he said that he didn't know if he could wind a secondary that would be 5.5V, but maybe I misunderstood him.

Kofi

Sheldon

quote:

Originally posted by Kofi Annan
Why would it make a difference with the resistor divider in there? Just keeping things in balance?Kofi

Yes. With the resistor on one end only there will be a slight difference in potential from one end of the filament to the other. With the resistor divider, the filament will vary from middle to each end, or balanced, and the voltage delta from highest to lowest on the filament will be 1/2. Does it matter? Don't know.

quote:

Originally posted by Kofi Annan
More questions (that was fast!):

The 5.5V secondary on the PSU, is that for real? When I talked to Jack he said that he didn't know if he could wind a secondary that would be 5.5V, but maybe I misunderstood him.

Kofi

It doesn't have to be too exact. Err on the high side. You can always drop a little voltage with series resistance.

Sheldon

Kofi Annan

quote:

Makes sense to me.

quote:

It doesn't have to be too exact. Err on the high side. You can always drop a little voltage with series resistance.

Will do, but I now have a bit of a dilemma. Jack Eliano took a look at the schematic for the modified DRD and is not thrilled about it. He seems to think that there are some issues with the design and is advising that I go with the original DRD circuit he has posted on his site.

Jack seems very honest and I don't think he'd try and steer me wrong, but I also know that he's quite opinionated and is bit upset that someone has toyed with the original DRD design.

Now, I'm just trying to play the middle here and I don't want to make any waves, but his opinion (his opinion) is that the Thorsten design is far too complicated in the PSU and has some unnecessary additions in the audio circuit that could cause some instability.

Now, I am of the "if it sounds good..." camp, so I'd be willing to bet that both of these sound great, but I am also trying to learn something here, so let me make available the "Jack" side of the equation.

--THE OPINIONS ESPOUSED BELOW DO NOT NECESSARILY REPRESENT THOSE OF STAFF AND MANAGEMENT AT THE UNITED NATIONS, PARTICULARLY NOT NECESSARILY THOSE OF ONE KOFI ANNAN--

He first mentioned that he thought this circuit would cause a few problems as the bias point for the 300b and the D3a would be feed another. I believe what he means is that if you just want to adjust the bias point of the 300b, you're going to end up adjusting the bias point of the D3a as well. Moreover, he thought that the driver tube should have about 15mA and 200V to eliminate the Miller effect on the 300b at frequencies below 20KHz.

You can tell these ain't Kofi's words, right?

Here's just some of the rants I was able to scribble down. Jack sez:

1. The common mode chokes in the PSU are only for filtering RF frequencies and are unnecessary, unless you live near an arc welding factory.

2. Elevating the D3a filament by strapping it to the B+ is also unnecessary.

3. The paralleling of caps coming off the 300b cathode are unnecessary-- no audible difference between one 50uF - 100uF cap (depending on desired bass roll-off) and the multiple paralleled nanofarad caps.

4. The parallel caps coming off the choke load can be done away with entirely with the other end of the choke strapped to the top of the paralleled 7K5 resistors.

5. Given scenario 4, the 300b should be biased with a 5K variable resistor and adjusted so that it sees 220V and 85mA across it. The resistor network coming off the 300B cathode can then be dispensed with.

In a nutshell, I think Jack was concerned that there were modifications made to a circuit that had his name on it, although he was quick to mention that the DRD circuit is not really new--- it just a modified Lofton-White (I'm sounding studious here, I know). The important thing for me is that I really, really want to learn. I learn most by doing and I would like to get this amp project rolling.

I am compelled by what Jack had to offer and I think I could learn a lot by asking for comments on his comments. I know this will likely ruffle some feathers and I don't mean to do that. Hell, I don't really understand half of what he said, but I know this will make for some interesting discussion, so here it is in print.

So, have at it. Let me know what you think of Jack's comments. But remember, that I'm just a schmuck who's trying to sort all this out.

Jeez. This makes the cousin thing seem trivial.

Thine,
Kofi

Sheldon

This ain't so hard. Build it Jack's way first, since that's simpler. Then, as you have the time and inclination modify one element at a time (adding a common mode choke, for instance) and see if you like it better or not, etc.. I didn't do a careful analysis, but I don't think anything in the original design forecloses the option of making all the mods to the posted design at very little additional cost. This way you will learn the most important thing - what YOU like.

Or, just ignore Jack and build whatever you want. BTW, he tried to talk me out of my present project, but I'm keen to try it anyway. Still he's fun to talk to.

Sheldon

ligascon

Hi people,

Yes Kofi, things get complicated and then you start whishing that your cousin was around...

I wish I could anwser to the issues that Jack brings to the table but as you could have probably guessed, I don�t have the background.

I only built an amp following the ideas of someone that showed himself totally helpful and then I shared the process with you guys because the thing has sounded great since day 1 and continues to do so without a glitch.

Maybe big brother T. himself is watching how this whole thing unveils. Also, maybe is time that he could bring some discurssion items to our table...

As for now I will take a chance and quote some of the info that he gave me about the amp. Hope that it helps. Here it is:

quote:

I would recommend you try a 350V/60mA/5K operating point for the 300B.

Please start by reading this:

http://diyaudio.com/forums/showthre...&threadid=31858

Especially the later parts.

http://diyaudio.com/forums/showthread.php?postid=372236

I will be using the parts numbers (Rx�, Cx�) from the original post (see the pentode driver circuit attached to the thread) as most applies equally to the �monkey� (aka DRD)

Then look at the 437aA/300B circuit here:

http://www.fortunecity.com/rivendel...fiertheory.html

First, our B+ will be 350 (300B Vak) + 74V (300Vgk) = 175 (D3a Vak) + 599V.

I normally assume the Choke in the Monkey circuit to have around 1200 Ohm DCR, this is based on the S&B 160H/12mA Choke I had designed for my use in such circuits. We want not too much current through the D3a, to stop it from sounding too harsh and gritty; 10mA is a good starting point. So 10mA * 1200 Ohm = 12V of the Bias for the 300B will be developed across the Choke. This leaves 74V � 12V = 62V for the cathode resistor. With 62V/60mA we get a 1K Cathode resistor R3, which will dissipate around 4 Watt, so a 9 Watt or 12 Watt type should be used.

Looking at my D3a datasheets, we have nice triode curves, 175V/10mA is around 2V Bias, so the grid of the 300B and the anode of the D3a will be at 177V. A current of 60mA will flow through the D3a cathode resistor R1 and will generate 2V Bias, so 33 Ohm are nominal. The specific value will have to be adjusted in circuit for the specific valve used, so please fit a 100R Trimmer (1 Watt cermet multiturn recommended) with a 10R series resistor plus a 100R parallel resistor, giving around 10-50Ohm adjustment range.

This leaves R2 to be calculated. With 10mA flowing through the D3a, it will have draw 50mA current with 175V + 12V = 187V across it, so 187V/50mA = 3740 Ohm, suggesting 2 pieces 7K5 resistors in parallel. Each will dissipate around 5 Watt, so 9 Watt or 12 Watt types should be used.

Alternatively, if you can find a 5K1 or 5K6 very large �adjustable tap� wire wound resistor with a least 2 taps and at least 50W dissipation rating will make the amplifier easily adjustable for different operating points and Output valves if you like.

The capacitor across R2 shown in the original �monkey� schematic should be retained but can be smaller in value, around 10-15Uf will do.

The final B+ must also account for our 2V Bias for the D3a and the losses in the output transformer so I�d call for around 620V per channel.

For the 15uF and 50uF capacitors, baseline would be decent quality encased oil filled Motor Run Capacitors. You can get them in 50uF & 15UF for very little money and they better many audiophool types. I�d put a good quality C/16.18 Foil&Film Bypass (3uF for the 50uF & 1uF for the 15uF) with further bypassing with C/16.18 Polystyrene Foil (220nF and 68nF) followed with another C/16.18 Capacitor (15nF and 4,7nF) in either Silver Mica or Polystyrene.

Hope that you find it helpful. Take much care,

Luis

Kuei Yang Wang

Hi,

quote:

Originally posted by Kofi Annan
Will do, but I now have a bit of a dilemma.

A bit of history (yes, I know that is HisStory).

My Circuit actually grew seperate to the DRD and parallel (check the Joe List archives). Hence my circuit is NOT a modified DRD. It is a seperate complete development.

I have of course since seen the DRD. I think that Jack Elliano is looking for different qualities and has different design approaches. An example is that he invarably runs output valves at max dissipation, something I fiond to generate much worse sound than possible from the output valve.

I suggest that you stick one design. By all means build Jacks circuit, but his COMPLETE CIRCUIT EXACTLY as he shows. Or build mine and then EXACTLY as I suggest.

As you have seen it fit to make Jacks criticsm of my circuit public I will answer the points raised.

Jack Eliano took a look at the schematic for the modified DRD and is not thrilled about it. He seems to think that there are some issues with the design and is advising that I go with the original DRD circuit he has posted on his site.

quote:

Originally posted by Kofi Annan
He first mentioned that he thought this circuit would cause a few problems as the bias point for the 300b and the D3a would be feed another.

He is wrong. The circuit contains the same positive feedback operating condition stabilisation as found in old Loftin White circuit. Unlike the DRD circuit the "Monkey" is not subject to the pinching off of anode current due to rise of cathode voltage when driven into high distortion. Hence the "instability" is actually an IMPROVED stability, over most other direct coupled circuits.

quote:

Originally posted by Kofi Annan
I believe what he means is that if you just want to adjust the bias point of the 300b, you're going to end up adjusting the bias point of the D3a as well.

The 300B operating point in my circuit is self adjusting, it SHOULD NOT be adjusted manuual.

quote:

Originally posted by Kofi Annan
Moreover, he thought that the driver tube should have about 15mA and 200V to eliminate the Miller effect on the 300b at frequencies below 20KHz.

Funny, his OWN circuit operates the input/driver valve at much LESS anode current than the D3a is operated in my circuit, so low current is good when he use it?

quote:

Originally posted by Kofi Annan
1. The common mode chokes in the PSU are only for filtering RF frequencies and are unnecessary, unless you live near an arc welding factory.

The difference is actually visible on a 'scope and noise is not just generated by arc welding factories, but also by rectifiers, switched mode supplies, mobile phones, whashing machines, fridges and other modern conveniences...

quote:

Originally posted by Kofi Annan
2. Elevating the D3a filament by strapping it to the B+ is also unnecessary.

He is wrong. I have found more then a few cases where individual samples of valves showed significant heater/cathode noise leakage, meaning very unusal hum pattern where observed when these valves where AC heated.

By elevating the heater of ANY AC heated valve (I even fo this for EL34's and KT88's in my modified Shanling Amplifiers) the parasitic heater/cathode diodes are reilably reverse biased, which reliably produces low noise with AC Heating AND reduced non-linear signal current leakage. I found the result of this little "tweak" quite significant in sonic terms.

quote:

Originally posted by Kofi Annan
3. The paralleling of caps coming off the 300b cathode are unnecessary-- no audible difference between one 50uF - 100uF cap (depending on desired bass roll-off) and the multiple paralleled nanofarad caps.

Actually, the paralleled capacitors perform what is called bypassing. Look it up. This is a contentious issue, having tried both options I ALLWAYS use bypass capacitors. Several people who buyild my designs and did the same comparison for themselves agree. Non who have ACTUALLY TRIED IT have said it made no difference.

quote:

Originally posted by Kofi Annan
4. The parallel caps coming off the choke load can be done away with entirely with the other end of the choke strapped to the top of the paralleled 7K5 resistors.

Then the circuit operation is altered in a way that reduces LF and HF bandwidth. I must councel AGAINST removing these capacitors in the strongest possible terms. It is in fact the WE Style decoupling found in the DRD Output stage and re-named by Jack "Ultrapath".

quote:

Originally posted by Kofi Annan
5. Given scenario 4, the 300b should be biased with a 5K variable resistor and adjusted so that it sees 220V and 85mA across it. The resistor network coming off the 300B cathode can then be dispensed with.

That will result in an Elliano DRD Amplifier.

I personally do not think that either the operating point for the 300B offers that good sound quality. It is worth noting the Ron Welborne's DRD Kits also use a lower dissipation opertaing point for better sound. Also, because it is an operating condition at the limit of dissipation the adjustment is needed to avoid exceeding the valves maximum dissipation for valves at the edge of tolerance are not killed quickly.

My circuit does not require adjustment other than for the D3a tolerance as the Output Valve is operated under condition that give less power but in stead are optimised for best sound from the 300B.

quote:

Originally posted by Kofi Annan
In a nutshell, I think Jack was concerned that there were modifications made to a circuit that had his name on it

Actually, that Circuit is NEITHER a modification of Jack's circuit nor does it (or shouyld it have) Jacks name on it.

I do not think that his criticisms where based on actually trying to un derstand why I had made the circuit design as I have, but rather to assert that the Circuit should be like his circuit.

Allow me to assert that my circuit should be like my circuit, as I have very good reasons for each and every feature in it.

Sayonara

Gluca

KYW,

most probably you expressed your thougths, ideas and experience several times in the past but unfortunately I missed your older posts on the subject. I had also a look to a link to a thread from yourself posted by Luis.

I would ask what are the pros in using a pentode as driver in this project. ... references to exisiting literature would be great.

Ciao. Grazie.
Gianluca

Kuei Yang Wang

Konnichiwa,

quote:

Originally posted by Gluca
I would ask what are the pros in using a pentode as driver in this project. ... references to exisiting literature would be great.

The Pentode is wired as Triode. It is a compromise, as the D3a is readily available NOS and sounds good used that way. No readily available true triodes with similar performance are around.

True Pentodes as Drivers have some advantages too, it is really a matter of swings and roundabouts.

Sayonara

tubelab.com

As it is becomming obvious here there are many opinions as to how tube amplifiers should be built. In this case I don't have an opinion because I have not built either of these designs, or anything that resembles either of these designs. I try to avoid getting into any type of "what kind of amplifier should I build" discussion unless I have direct experience with one of the designs.

Since there are more than two amplifier designs in the world, as soon as you recommend a design, you will be outnumbered by people recommending a "better" design.

I have had a few conversations with Jack, as have some of my friends, and we have come to the same conclusion, that he is somewhat "old school" and he is a person of strong opinion. He definitely does not like sand in the audio path, and doesn't like mosfet drive. I do. That does not make either of us, or our designs bad, just different. That gives you guys more circuits to build, and unfortunately (for some) more choices to make.

What is of generally accepted opinion is that his transformers are liked by everybody who uses them. One thing that he told me is that if you only need a single speaker impedance (like 8 ohms) he can wind the transformer with only one secondary. This makes the transformer cheaper, and allows better high frequency response.

fred76

Hi Kofi,

quote:

1. The common mode chokes in the PSU are only for filtering RF frequencies and are unnecessary, unless you live near an arc welding factory

It's interesting to note that Welborne's new DRD based kit amps using Electraprint iron (Terraplane 300B and 45 Starchief) now feature common mode chokes for the filament supplies... So maybe it's just a matter of opinion?

http://www.welbornelabs.com/images/terraschematic.jpg

from Ron Welborne's site:

"Not being able to remove the electrolytic capacitors from the 300B's filament supply without increasing the noise level leaves one looking for other solutions. We are already using Schottky diodes and a CLC power supply in our DRD design which was a phenomenal improvement over the typical CRC supply and even supplies utilizing current source regulators. However I felt the filament supply was still a source, or path, for noise to enter the audio signal. So I decided to add an additional stage of filtering and one in the form of a Common Mode Choke. Through extensive testing I'm now certain this additional choke is effectively filtering the remaining vestiges of electrolytic noise, diode switching noise and rf noise."

arnoldc

re: Jack Eliano 300B DRD

My friend had mono blocks made by Jack Elliano himself. I borrowed it and had a listen on my system in my room. One thing i immediately noticed is it sounded quite different from other 300Bs I've heard. It sounded so clean and quiet and leaner, maybe bordering or on the clinical/analytical side. It's not bad per se, but matter of taste for the listener.

Here's the picture of the Jack Eliano 300B DRD (the biggest of the two mono blocks), TS Audio DC 300B (the smaller of the two mono blocks), and the ugly amp in the center was my prototype for a DC'ed 2A3.

Kofi Annan

quote:

Yes Kofi, things get complicated and then you start whishing that your cousin was around...

Tell me about it.

quote:

I only built an amp following the ideas of someone that showed himself totally helpful and then I shared the process with you guys because the thing has sounded great since day 1 and continues to do so without a glitch.

I know it. Thorsten helped me with his phono pre project and I'm very thankful for it. I listen to it every day and love the results.

quote:

My Circuit actually grew seperate to the DRD and parallel (check the Joe List archives). Hence my circuit is NOT a modified DRD. It is a seperate complete development.

I believe you, I really do. The last thing in the world I want to do is to start a war here, but I feel like I've already done that. Jeez. I'm really sorry that I've brought this on...

quote:

I think that Jack Elliano is looking for different qualities and has different design approaches. An example is that he invarably runs output valves at max dissipation, something I fiond to generate much worse sound than possible from the output valve.

I agree about running it at max dissipation. I was really surprised at how "hot" this is running. 410V across the 300b is kinda pushing it, but Jack maintains that this is the proper voltage to get the lowest possible distortion out of the valve.

quote:

As you have seen it fit to make Jacks criticsm of my circuit public I will answer the points raised.

I really debated my last post for some time. I knew that it could possibly upset you and the masses, but I thought this would make for a good learning tool for me. I guess that's selfish and maybe I shouldn't have posted Jack's comments, but I thought bringing the differences to the forefront would facilitate a deeper understanding of both topologies and the design philosophies therein. Very sorry if I upset the basket here.

quote:

The circuit contains the same positive feedback operating condition stabilisation as found in old Loftin White circuit. Unlike the DRD circuit the "Monkey" is not subject to the pinching off of anode current due to rise of cathode voltage when driven into high distortion. Hence the "instability" is actually an IMPROVED stability, over most other direct coupled circuits.

OK-- this is the type of thing I'm talking about. Good information.

quote:

Funny, his OWN circuit operates the input/driver valve at much LESS anode current than the D3a is operated in my circuit, so low current is good when he use it?

This may be due to a misunderstanding on my part. I thought that he had used both sides of the 6N1P simultaneously to get what he felt was the proper amount of mA for the 300B.

quote:

Hey-- we have a washing machine! Mrs. Annan operates it all the time to clean my two shirts and pair of pants. Makes sense about the interference, though...

quote:

OK-- good news on this.

quote:

Good to know. Understood.

quote:

Really pushing the "quote" limit here, but there's a reason. Hang on...

quote:

I personally do not think that either the operating point for the 300B offers that good sound quality. It is worth noting the Ron Welborne's DRD Kits also use a lower dissipation opertaing point for better sound. Also, because it is an operating condition at the limit of dissipation the adjustment is needed to avoid exceeding the valves maximum dissipation for valves at the edge of tolerance are not killed quickly.

So noted.

quote:

I do not think that his criticisms where based on actually trying to un derstand why I had made the circuit design as I have, but rather to assert that the Circuit should be like his circuit.

Agreed. I tried to make this plain in my earlier post, but I failed.

quote:

Allow me to assert that my circuit should be like my circuit, as I have very good reasons for each and every feature in it.

I know that's true.

I'd like to say this: I have had nothing but wonderful experiences here on DIYAudio and I'd like them to continue. It was never my intention to start a war of philosophy where thousands of people die needlessly, but I may have done just that.

I just wanted to understand the difference between the two topologies and I guess what I'm really asking is, what is the difference between the two philosophies?

Talking to Jack for even a few minutes (which is hard on the ears sometimes) yields an understanding that he is an engineer that truly believes in Measurement �ber Alles, that is, if it measures good, it is good. That's good until it measures good and sounds bad, which is possible. Just look at measurements for some full-range driver enclosure design and you'll know what I'm talkin' 'bout.

Thorsten-- I believe that your design measures and sounds fantastic. The point of my post was not to pit one against another, although it might make for great reality television. The point was to get at the soul behind topologies and to gain an understanding of both, which may have been a mistake.

Sorry for causing distress.

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I have had a few conversations with Jack, as have some of my friends, and we have come to the same conclusion, that he is somewhat "old school" and he is a person of strong opinion. He definitely does not like sand in the audio path, and doesn't like mosfet drive. I do. That does not make either of us, or our designs bad, just different. That gives you guys more circuits to build, and unfortunately (for some) more choices to make.

Yep. That's Jack. And you nailed the crux of the issue!

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Good point!

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My friend had mono blocks made by Jack Elliano himself. I borrowed it and had a listen on my system in my room. One thing i immediately noticed is it sounded quite different from other 300Bs I've heard. It sounded so clean and quiet and leaner, maybe bordering or on the clinical/analytical side. It's not bad per se, but matter of taste for the listener.

Second verse: same as the first.

Anyway. Hope I didn't cause too much turmoil here. Thanks for putting up with me.

Kofi

Sheldon

Gee Kofi, I'da thought with all the wars and grumpy people you deal with every day, Including our new appointee, that these minor (very minor) conflagrations would'nt even register. Breath in, slowly, slowly. Now breath out, slowly. Repeat, repeat, rinse. Relax it's only audio. Besides, it ain't you. Just read the tag line for diyAudio and calibrate your alarms accordingly.

Sheldon

Kuei Yang Wang

Konnichiwa,

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Originally posted by Kofi Annan
I agree about running it at max dissipation. I was really surprised at how "hot" this is running. 410V across the 300b is kinda pushing it, but Jack maintains that this is the proper voltage to get the lowest possible distortion out of the valve.

Yes, if you run the 300B at maximum dissipation you will get lower distortion at high power. When I design Amplifiers I tend to look not neccesarily for minimum distortion at maximum power, but for other parameters, such as the amount and spectrum of distortion at one Watt and below. And I derive my operating points unltimaly from listening combined with traditional analysis.

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Originally posted by Kofi Annan
I really debated my last post for some time. I knew that it could possibly upset you and the masses, but I thought this would make for a good learning tool for me.

Well, I am not upset. However, Jack made these comments personally to you, in private. You may have been better off dropping an e-mail with your concerns directly to me and keep the discussion out of the public domain.

I do respect what Jack does and have learnd much from his designs (including the fact that I do not like his approach that much) and I'd hate to be seem badmouthing his stuff.

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Originally posted by Kofi Annan
This may be due to a misunderstanding on my part. I thought that he had used both sides of the 6N1P simultaneously to get what he felt was the proper amount of mA for the 300B.

His original design from VTV used the 6AQ8, sections in parallel and at around 8mA total current....

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Originally posted by Kofi Annan
I just wanted to understand the difference between the two topologies and I guess what I'm really asking is, what is the difference between the two philosophies?

I think Jack is primarily concerned about technical aspects of performance. This includes quite agressive distortion cancellation between stages to get low THD but higher than average levels of odd order distortion and reduced even order levels, a type of distortion that sounds generally dissonant with music.

I personally try to understand how measured performance correlates with percieved good sound and listen long and hard myself for many fundamental things (like the 350V/60mA/5K Load operating point for the 300B) and often accept that good measurements do not reliably equate to good sound.

For example many years ago I modified my first zero feedback 300B PSE Amplifier from my initial build which used a lot of inverse predistortion for 20W out with low THD. Over time I removed this progressivley and as the THD went up the sound became better. For a short while I was willing to subscribe to "more distortion sounds good" thesis, which I also rejected eventually.

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Originally posted by Kofi Annan
Thorsten-- I believe that your design measures and sounds fantastic.

I doubt it measures overly good in the traditional sense, that was not my design goal. As for sound, ask Luis.... ;-)

Sayonara